Markers are often used in the medical field to indicate a location where tissue (e.g., from a tumor) has been collected from a patient. The marker, and therefore the tissue collection site, can be subsequently located using imaging techniques like x-ray, ultrasound, or magnetic resonance imaging (MRI).
A variety of markers and devices for marking a tissue location are available in the medical field. Typically the markers are pre-fabricated in an assortment of shapes and sizes, and then the markers are delivered to a tissue location using a delivery device.
For example, U.S. Pat. No. 6,575,991 describes a device for percutaneous marking of a lesion. The device includes a cannula and a stylet having a shaft and a base. In use, the stylet shaft extends through a guide passage and into the interior of the cannula, while the stylet base remains outside of the cannula. The device further includes a plunger configured to move the stylet within the cannula and eject a marker into a lesion site. The marker is pre-shaped prior to being loaded into a marker recess of the cannula. The marker has one of several shapes, including a spiral, star-burst, y-shape and horseshoe shape. However, because the marker is pre-fabricated outside of the cannula, it must be sized to slide within the inner passage. Therefore, the marker is not specially sized and shaped for a particular cannula, nor does the marker fit snugly into the end of the cannula, for example. The marker thus may slide within the cannula and slip out before it can be properly injected into a tissue site. In addition to having a potentially disadvantageous size, the shape of the marker may cause it to catch on or become tangled with the stylet, thereby preventing or interfering with the injection.
Another device for marking tissue within a human body is described in U.S. Pat. No. 6,228,055. The device includes a marker and an apparatus for delivering the marker to a location within the human tissue. The apparatus includes a tube that is guided to the tissue location. In one embodiment, a second region of the tube includes a forming die, which forms the marker into a predetermined shape, such as a helix. An important feature of this invention is the ability to use markers having a variety of shapes in order to identify different locations in a tissue. However, the markers are either prefabricated, then inserted into a lumen, or a special die is incorporated into each delivery device and used to form the marker. As such, unnecessary steps and components are required to make and use the device, so it is unnecessarily costly.
In general, markers that are prefabricated then inserted into a lumen or cannula according to methods of the related art are costly. These approaches typically require machining processes that are designed for very small parts with very tight tolerances, and both of those items tend to drive costs higher.
In addition, one way to prevent a marker from slipping out of an end of a device is to plug the end with a biocompatible substance, for example, bone wax. Another way to prevent the marker from slipping out is to use a spacer between the plastic hubs of the cannula and the stylet, so that, before use, the marker is able to move in between the bone wax and the stylet, but not outside of those bounds. When a doctor or other user is ready to deliver the marker, the spacer is removed and the marker and bone wax are then pushed into the patient. However, the use of bone wax introduces another foreign material into the tissue site, which may increase the risk of potential infections or adverse events.
There is a need in the art for a devices, kits and methods of making a marker element that is less costly than known devices and methods. In one aspect, the marker element should be formed within the delivery device so that it is uniquely shaped and sized for a particular device to provide seamless and reliable delivery of the marker element to a tissue location.